Roadrunner tire size

What's biggest widest tallest tire I can fit 69 rrnot tubbed

You will find a lot of discussion here about this if you do a search but I will tell you what is on my 69. I have 275/60/15's on wider than stock wheels, I don't know the wheel size or back spacing. I had a passenger in the Rt rear last Sunday and the right tire just kissed the outside wheel well once....Ed